The present invention relates to motor-vehicle structures, for example for commercial vehicles, vans, buses or the like, of the type comprising a metal frame including a pair of longitudinal members connected by cross members and a metal cab body mounted on the frame and including a pair of longitudinal sub-cab members supported on the longitudinal members of the frame by means of elastic supports that enable relative movements in a vertical direction of the body with respect to the frame.
The object of the present invention is to provide a motor-vehicle structure of the type referred to above provided with a front module constituted by elements made of plastic and/or composite material, which will have a reduced number of components, will be particularly light, and will guarantee good characteristics both from the standpoint of resistance to impact and from the standpoint of ease and rapidity of assembly.
With a view to achieving the above purpose, the subject of the invention is a motor-vehicle structure having the characteristics described below, including a motor-vehicle structure comprising:                a metal frame, including a pair of longitudinal members connected by cross members;        a metal cab body mounted on the frame, including a pair of longitudinal sub-cab members supported on the longitudinal members of the frame by means of elastic supports that enable relative movements in a vertical direction of the body with respect to the frame;                    a front metal cross member for absorption of impact, fixed to the front ends of the two longitudinal members of the frame;            a main front metal plate connected to the front end of each longitudinal frame member, facing a respective auxiliary front metal plate connected to the front end of a respective longitudinal sub-cab member, to distribute the forces applied by the front cross member between the longitudinal members of the frame and the longitudinal sub-cab members; and                        a front subassembly or module made up of elements made of plastic, composite material, or both plastic and composite material, fixed to the cab body and defining the front part of a bodywork of the motor vehicle.        
The subject of the invention is also a method for assembly of a motor-vehicle structure of the type specified above and described below, including a method for assembly of a motor-vehicle structure as mentioned directly above, wherein the cab body is subjected to painting, after which the front subassembly or module is assembled thereon by means of successive assembly of the components made of plastic and/or composite material that constitute it, the cab body being coupled to the frame of the motor vehicle in an intermediate step of the operations of assembly of the various components constituting the front subassembly or module.